target: Drop se_device TCQ queue_depth usage from I/O path

Historically, pSCSI devices have been the ones that required target-core
to enforce a per se_device->depth_left.  This patch changes target-core
to no longer (by default) enforce a per se_device->depth_left or sleep in
transport_tcq_window_closed() when we out of queue slots for all backend
export cases.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Roland Dreier <roland@purestorage.com>
Cc: Joern Engel <joern@logfs.org>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

4 files changed, 2 insertions, 46 deletions

diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index 1f74de25a92f..0c5992f0d946 100644
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -1132,8 +1132,6 @@ int se_dev_set_emulate_rest_reord(struct se_device *dev, int flag)
  */
 int se_dev_set_queue_depth(struct se_device *dev, u32 queue_depth)
 {
-        u32 orig_queue_depth = dev->queue_depth;
-
         if (atomic_read(&dev->dev_export_obj.obj_access_count)) {
                 pr_err("dev[%p]: Unable to change SE Device TCQ while"
                         " dev_export_obj: %d count exists\n", dev,
@@ -1167,11 +1165,6 @@ int se_dev_set_queue_depth(struct se_device *dev, u32 queue_depth)
         }
 
         dev->se_sub_dev->se_dev_attrib.queue_depth = dev->queue_depth = queue_depth;
-        if (queue_depth > orig_queue_depth)
-                atomic_add(queue_depth - orig_queue_depth, &dev->depth_left);
-        else if (queue_depth < orig_queue_depth)
-                atomic_sub(orig_queue_depth - queue_depth, &dev->depth_left);
-
         pr_debug("dev[%p]: SE Device TCQ Depth changed to: %u\n",
                         dev, queue_depth);
         return 0;
diff --git a/drivers/target/target_core_pscsi.c b/drivers/target/target_core_pscsi.c
index b73a399cdd54..d35467d42e12 100644
--- a/drivers/target/target_core_pscsi.c
+++ b/drivers/target/target_core_pscsi.c
@@ -350,7 +350,6 @@ static struct se_device *pscsi_add_device_to_list(
          * scsi_device_put() and the pdv->pdv_sd cleared.
          */
         pdv->pdv_sd = sd;
-
         dev = transport_add_device_to_core_hba(hba, &pscsi_template,
                                 se_dev, dev_flags, pdv,
                                 &dev_limits, NULL, NULL);
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 1cc7e920ab0b..7c2def7e2593 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -691,12 +691,6 @@ void transport_complete_task(struct se_task *task, int success)
         struct se_cmd *cmd = task->task_se_cmd;
         struct se_device *dev = cmd->se_dev;
         unsigned long flags;
-#if 0
-        pr_debug("task: %p CDB: 0x%02x obj_ptr: %p\n", task,
-                        cmd->t_task_cdb[0], dev);
-#endif
-        if (dev)
-                atomic_inc(&dev->depth_left);
 
         spin_lock_irqsave(&cmd->t_state_lock, flags);
         task->task_flags &= ~TF_ACTIVE;
@@ -971,9 +965,8 @@ void transport_dump_dev_state(
                 break;
         }
 
-        *bl += sprintf(b + *bl, "  Execute/Left/Max Queue Depth: %d/%d/%d",
-                atomic_read(&dev->execute_tasks), atomic_read(&dev->depth_left),
-                dev->queue_depth);
+        *bl += sprintf(b + *bl, "  Execute/Max Queue Depth: %d/%d",
+                atomic_read(&dev->execute_tasks), dev->queue_depth);
         *bl += sprintf(b + *bl, "  SectorSize: %u  MaxSectors: %u\n",
                 dev->se_sub_dev->se_dev_attrib.block_size, dev->se_sub_dev->se_dev_attrib.max_sectors);
         *bl += sprintf(b + *bl, "        ");
@@ -1328,9 +1321,6 @@ struct se_device *transport_add_device_to_core_hba(
         spin_lock_init(&dev->se_port_lock);
         spin_lock_init(&dev->se_tmr_lock);
         spin_lock_init(&dev->qf_cmd_lock);
-
-        dev->queue_depth        = dev_limits->queue_depth;
-        atomic_set(&dev->depth_left, dev->queue_depth);
         atomic_set(&dev->dev_ordered_id, 0);
 
         se_dev_set_default_attribs(dev, dev_limits);
@@ -1982,18 +1972,6 @@ static void transport_set_supported_SAM_opcode(struct se_cmd *se_cmd)
         spin_unlock_irqrestore(&se_cmd->t_state_lock, flags);
 }
 
-static inline int transport_tcq_window_closed(struct se_device *dev)
-{
-        if (dev->dev_tcq_window_closed++ <
-                        PYX_TRANSPORT_WINDOW_CLOSED_THRESHOLD) {
-                msleep(PYX_TRANSPORT_WINDOW_CLOSED_WAIT_SHORT);
-        } else
-                msleep(PYX_TRANSPORT_WINDOW_CLOSED_WAIT_LONG);
-
-        wake_up_interruptible(&dev->dev_queue_obj.thread_wq);
-        return 0;
-}
-
 /*
  * Called from Fabric Module context from transport_execute_tasks()
  *
@@ -2126,16 +2104,7 @@ static int __transport_execute_tasks(struct se_device *dev)
         struct se_task *task = NULL;
         unsigned long flags;
 
-        /*
-         * Check if there is enough room in the device and HBA queue to send
-         * struct se_tasks to the selected transport.
-         */
 check_depth:
-        if (!atomic_read(&dev->depth_left))
-                return transport_tcq_window_closed(dev);
-
-        dev->dev_tcq_window_closed = 0;
-
         spin_lock_irq(&dev->execute_task_lock);
         if (list_empty(&dev->execute_task_list)) {
                 spin_unlock_irq(&dev->execute_task_lock);
@@ -2146,10 +2115,7 @@ check_depth:
         __transport_remove_task_from_execute_queue(task, dev);
         spin_unlock_irq(&dev->execute_task_lock);
 
-        atomic_dec(&dev->depth_left);
-
         cmd = task->task_se_cmd;
-
         spin_lock_irqsave(&cmd->t_state_lock, flags);
         task->task_flags |= (TF_ACTIVE | TF_SENT);
         atomic_inc(&cmd->t_task_cdbs_sent);
@@ -2170,7 +2136,6 @@ check_depth:
                 spin_unlock_irqrestore(&cmd->t_state_lock, flags);
                 atomic_set(&cmd->t_transport_sent, 0);
                 transport_stop_tasks_for_cmd(cmd);
-                atomic_inc(&dev->depth_left);
                 transport_generic_request_failure(cmd);
         }
 
diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index 28190dc10eef..cd4caf3a598f 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -798,7 +798,6 @@ struct se_device {
         spinlock_t              stats_lock;
         /* Active commands on this virtual SE device */
         atomic_t                simple_cmds;
-        atomic_t                depth_left;
         atomic_t                dev_ordered_id;
         atomic_t                execute_tasks;
         atomic_t                dev_ordered_sync;